Colluvium is a natural deposit of soil and rock. The physico-mechanical properties of colluvium are controlled to a large extent by its structure. On the basis of ground investigation and laboratory grading analysis

large scale direct shear tests on remoulded colluvium samples are carried out in laboratory. The shear stress-strain curves and shear strengths of colluvium with different rock particle contents

rock particle shapes

soil types and stress states are obtained. In addition

studies of the deformation and strength characteristics of colluvium are performed and a nonlinear increasing trend in shear strength of colluvium with respect to an increase in rock particle contents is first proposed. The results indicate that the shear stress-strain curve of colluvium is different from that of homogeneous soil or rock. Colluvium samples exhibit shear dilatation characteristics at low normal stress levels and tend to have a transformation from shear contraction to dilatation at higher stress levels. Overall

the shear strength of colluvium increases with increasing content of rock particles

for which the trend of increase is slow at first

and then becomes rapid

and slow down finally. The increment of internal friction angle increases linearly with the increase of the rock particle contents (0-80% for cohesive colluvium and 40%-80% for cohesionless colluvium). With the same content of rock particles

the internal friction angle of colluvium containing rock particles with irregular shape is higher than that composed of rock particles with regular shape.